The only criticisms we have are that the fit can create a suction feeling in your ears, especially when you use the button controls. (thewirecutter.com)
If the palate is involved, then the baby may not be able to create the suction needed for breastfeeding. (articles.chicagotribune.com)
The motor create suction, so you won't have to work hard to express enough milk. (followmum.com)